Joint or coupling device incorporating a mechanically-induced weak point and method of use

ABSTRACT

A system and method using liner joints, pup joints, couplings, or similar components incorporating a mechanically-induced weak point to access targeted subterranean rock formations. More particularly, the mechanically-induced weak point may comprise a machined weakness, blow-out plug, burst disc, soluble plug, or the like. The mechanically-induced weak point may be adapted to burst at a predetermined blow-out pressure differential. Alternatively, the soluble plug may be manufactured of soluble material adapted to selectively dissolve in certain solutions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit to U.S. Provisional Patent Ser. No. 61/221,414, filed on Jun. 29, 2009 by Lyle Laun, and titled “SYSTEM AND METHOD FOR MULTI-STAGE HYDRAULIC FRACTURE STIMULATING BY USE OF A LINER JOINT OR PUP JOINT INCORPORATING A MECHANICALLY INDUCED WEAK POINT (MACHINED WEAKNESS, BLOW-OUT PLUG(S), OR ACID SOLUABLE PLUG(S) INSTALLED) OR A LINER JOINT COUPLING DEVICE INCORPORATING A SIMILAR STYLE OF MECHANICALLY INDUCED WEAK POINT,” the entire contents of which are hereby incorporated by reference.

BACKGROUND

1. Field of the Disclosure

The present disclosure relates generally to subsurface oil and gas wells, and in particular, to an apparatus and method for accessing targeted subterranean rock formations by use of liner joints, pup joints, or couplings incorporating one or more mechanically-induced weak points.

2. Description of the Related Art

Hydraulic fracturing is typically employed to create additional passageways or otherwise increase the permeability of underground rock formations to facilitate flow through the formation to a producing well. Typically, fracturing may be accomplished by injecting a fluid containing sand or other proppant under sufficient pressure to create fractures in the rock. In cases where a well has a well liner or casing installed, the well liner is typically perforated prior to fracturing. Perforation helps create one or more holes through the liner or casing and into a targeted rock formation, through which a fracturing fluid may be injected. The perforating and fracturing steps are carried out at one or more predetermined depths in the well to access the targeted rock formations.

Perforation may be accomplished by one of several known methods. For example, perforation may be carried out by injecting abrasive fluids under high pressure to cut a hole through the liner or casing. Another known method of perforation is carried out by lowering an explosive charge within the wellbore to the predetermined depth and detonating the charge, thereby penetrating the well liner or casing. An alternative to perforating is accomplished by dropping one or more actuating balls down the wellbore and increasing pressure in the well, which opens ports in the liner by mechanically activating them.

Known perforation methods may have certain disadvantages associated with them. For example, when perforating with abrasive fluid, the fluid is typically pumped down the well to the perforation location(s), circulated to the surface, re-mixed, and recycled down the well again. Carrying out an abrasive fluid perforation operation generally uses a large amount of fluid, which increases costs, such as costs to transport the fluid to and from the well location. Such transportation costs may increase substantially for wells at isolated locations or on rough terrain.

One disadvantage of using explosive charges is that this method of perforation may present safety concerns in transporting, storing, and preparing the explosive charges. Taking proper measures to mitigate such safety concerns may increase the costs associated with using explosive charges. Another disadvantage of using explosive charges is that the explosion may leave debris within the rock formation, which could potentially restrict the flow of production fluid through the targeted rock formation and into the well, thereby decreasing production.

The ball-drop method employs at least one ball seat and a corresponding port set at depths within a well near a targeted rock formation. In the ball-drop method, an actuating ball is dropped down the well from the surface and landed in its corresponding ball seat. For multiple ports within a well, each ball seat may be larger than other ball seats located down the well. Different-sized actuating balls correspond to different-sized ports in the well. In other words, the smallest actuating ball corresponds to the lowest port in the well, and each port above corresponds to a larger-sized actuating ball. When an actuating ball lands in its corresponding ball seat, it forms a seal. Fluid is pumped down the well creating a pressure differential across the seal formed by the actuating ball and ball seat. The pressure differential causes a sleeve to slide axially, which opens the corresponding port, thereby allowing access to the targeted rock formation. One potential disadvantage of this method is that it is not compatible with cemented well casings; thus it is typically employed in open hole wells. Open hole packers are typically used within open hole wells, which add significant equipment expenses compared to wells with cemented casing.

Another potential disadvantage of the ball-drop method is that each actuating ball is larger than the actuating ball(s) that correspond with the port(s) lower in the well. As a result, a practical limit exists to the quantity of ball-activated ports a well can have because of the size restrictions of the wellbore and actuating balls. Another potential disadvantage of the ball-drop method is that after dropping an actuating ball down the well and opening a port, the ball is typically milled out to allow for production from the well. Milling out each actuating ball may be time-consuming and costly.

The present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.

SUMMARY

An embodiment of the present disclosure is directed to a liner segment having a wall and a mechanically-induced weak point on the wall. The wall forms an inner bore and an outer surface. The mechanically-induced weak point is adapted to rupture at a predetermined pressure differential between the inner bore and the outer surface. The mechanically-induced weak point permits communication between the inner bore and the outer surface after the mechanically-induced weak point has ruptured.

The mechanically-induced weak point may be selected from the group consisting of a machined weakness, a blow-out plug, a burst disc, and a soluble plug. The mechanically-induced weak point may further include a port adapted to permit communication between the inner bore and the outer surface. The liner segment may include a coupling device. The liner segment may have centralizer ribs. The mechanically-induced weak point may be located on an outward-facing surface of at least one centralizer rib.

Another embodiment of the present disclosure is directed to a liner segment having a wall, a port on the wall, and a soluble plug. The wall forms an inner bore and an outer surface. The port on the wall is adapted to permit communication between the inner bore and the outer surface. The soluble plug is adapted to selectively prevent communication through the port. The soluble plug may comprise acid-soluble material.

Another embodiment of the present disclosure is directed to a method of well completion comprising hydraulically isolating an internal length of a wellbore liner that includes a mechanically-induced weak point, pumping a treatment medium into the hydraulically-isolated wellbore length, and increasing the pressure of the treatment medium within the hydraulically-isolated wellbore length to a predetermined pressure, thereby causing the mechanically-induced weak point to burst. The method may include locating the wellbore liner segment having the mechanically-induced weak point at a location in the well.

Yet another embodiment of the present disclosure is directed to a method of well completion comprising hydraulically isolating an internal length of a wellbore liner that includes a plug made of soluble material, and pumping a treatment medium into the hydraulically-isolated wellbore length, thereby causing the plug to partially dissolve. The method may include locating the wellbore liner segment having the plug at a location in the well. The plug may comprise an acid-soluble material. The treatment medium may comprise an acid-based solution. The method may further include increasing the pressure of the treatment medium within the hydraulically-isolated wellbore length, thereby causing the partially-dissolved plug to burst.

BRIEF DESCRIPTION OF THE DRAWINGS

This disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

FIG. 1 shows a liner joint having a machined weakness in accordance with an embodiment of the present invention;

FIG. 2 depicts a liner joint coupling device having a port with a blow-out plug inserted therein;

FIGS. 3A and 3B depict a blow-out plug;

FIG. 4 is a side view of a fluted coupling device having at least one mechanically-induced weak point;

FIG. 5 is an axial view of a fluted coupling device having one or more mechanically-induced weak points;

FIG. 6 is a cut-away side view of a coupling device having one or more burst discs;

FIG. 7 depicts a typical well completion using a liner joint having one or more machined weakness; and

FIG. 8 depicts a typical well completion using a liner joint coupling device having a port with a blow-out plug inserted therein.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that various changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.

The present disclosure relates to apparatus and methods for accessing targeted subterranean rock formations 170 (depicted in FIGS. 5, 7, and 8) by employing mechanically-induced weak points 200 on liner joints, pup joints, couplings, or the like. A mechanically-induced weak point 200 may comprise a machined weakness, a blow-out plug, a burst disc, a soluble plug, or any other corresponding structure recognized by one of ordinary skill in the art having the benefit of this disclosure. As disclosed herein, mechanically-induced weak points 200 may be employed to access targeted rock formations 170 prior to fracturing operations within subsurface oil and gas wells.

In the embodiment shown in FIG. 1, a liner joint 10 comprises a machined weakness 20. The machined weakness 20 comprises a weak point in the liner joint 10 created by known methods such as partially drilling through the liner wall, thereby removing material from the liner wall. Alternatively, a chemical etching process may be used to remove material from the liner wall of a liner joint 10, thereby creating a weak point. Alternatively, other known methods to reduce the structural strength of the liner wall may be used. The amount of material removed from the liner joint 10 may be dependent on a desired blow-out pressure differential, the material making up the liner joint 10, the thickness of the liner wall, or other factors.

A desired blow-out pressure differential may be determined by factoring an assortment of variables of the well, such as hydrostatic pressure, temperature, rock properties, cement type, and surface pumping pressure. A wide range of blow-out pressure differentials is obtainable, thereby allowing the well operator to meet specific needs and circumstances of the well.

The liner joint 10 may be selectively adapted to cause the machined weakness 20 to rupture after the pressure inside the liner joint 10 has exceeded the pressure outside the liner joint 10 by at least the desired blow-out pressure differential. When the machined weakness 20 ruptures, a hole is created that allows communication between the inside of the liner joint 10 and the targeted rock formation 170.

As depicted in FIG. 1, the liner joint 10 has threads 25 to secure the liner joint 10 to other liner joints, coupling devices, or other like components. As one of ordinary skill in the art would appreciate, the threads 25 may be any size, shape, or configuration that provides secured connection between liner components. In other embodiments, alternate connecting means may be employed to secure liner components together.

Some embodiments of the liner joint 10 include a mechanically-induced weak point 200 that comprises a pass-through port 40 (not depicted in FIG. 1), in which a blow-out plug 50 is seated (depicted in FIGS. 2, 3A, 3B, 5, and 8). As described above in relation to a predetermined blow-out pressure differential, the blow-out plug 50 may be selectively designed and fabricated to blow out in response to a predetermined differential between the internal and external pressures of the liner joint 10. In other embodiments, the mechanically-induced weak point 200 comprises a burst disc 140 (depicted in FIG. 6), a soluble plug 50, a machined weakness 20, or any other corresponding structure recognized by one of ordinary skill in the art having the benefit of this disclosure.

The mechanically-induced weak point 200 may be designed for unidirectional pressure blow-out. For example, the mechanically-induced weak point 200 may be adapted to burst if the internal pressure exceeds the external pressure by the predetermined blow-out pressure differential, but not burst if the external pressure is greater than the internal pressure.

Some embodiments of the liner joint 10 comprise multiple mechanically-induced weak points 200. The mechanically-induced weak points 200 may be oriented in a pre-determined fashion on the liner joint 10. For example, the mechanically-induced weak points 200 may be distributed in a radially-symmetrical fashion or along a helical line around the outer surface of the liner joint 10, or in any other conceivable pattern on the liner joint 10. A well operator may choose the distribution and location of machined weaknesses 10 to fit the circumstances of the targeted rock formation 170.

In some embodiments, a pup joint or short liner segment comprises one or more mechanically-induced weak points 200 as described above. Other similar liner components or joint types that comprise mechanically-induced weak points 200 fall under the scope of this disclosure.

In the embodiment depicted in FIG. 2, the liner joint coupling device 30 comprises a port 40 passing through its wall. The port 40 is sized to receive a blow-out plug 50 adapted to blow out of the port 40 at a predetermined blow-out pressure differential. One of ordinary skill in the art having the benefit of this disclosure is able to determine the size and material needed for a blow-out plug to achieve the desired blow-out pressure differential.

FIGS. 3A and 3B depict one potential design of a blow-out plug 50. The blow-out plug 50 shown in FIGS. 3A and 3B is tapered to provide unidirectional blow-out, as described above. It is to be understood that one of ordinary skill in the art having the benefit of this disclosure is able to design or obtain a blow-out plug 50 adapted to blow out at a desired blow-out pressure differential. In some embodiments, the liner joint coupling device 30 comprises a machined weakness 20, as described above in relation to FIG. 1.

In some embodiments, the blow-out plug 50 is manufactured from soluble material adapted to selectively dissolve in certain media. For example, a liner joint 10, liner joint coupling device 30, or pup joint may include an acid-soluble blow-out plug 50 that is adapted to dissolve when an acid-based fluid is circulated through the inside or outside of the liner joint 10 or liner joint coupling device 30. Such an acid-soluble blow-out plug 50 may allow communication through the port 40 after dissolution. Alternatively, the soluble blow-out plug 50 may be adapted to partially dissolve in the presence of certain solutions, which partial dissolution effectively lowers the blow-out pressure differential of the blow-out plug 50 to a predetermined blow-out pressure differential.

In the embodiment depicted in FIG. 4, the fluted coupling device 70 comprises one or more mechanically-induced weak points 200 as described above. The mechanically-induced weak points 200 comprise a machined weakness 20. Alternatively, the mechanically-induced weak points 200 may comprise blow-out plugs 50, burst discs 140, soluble plugs 50, or other corresponding structures as would be appreciated by one of ordinary skill in the art having the benefit of this disclosure. The fluted coupling device 70 further comprises radially-extending flutes or ribs 80. At least one mechanically-induced weak point 200 may be on the outward-facing surface 90 of a radial rib 80.

As depicted in FIG. 5, the ribs 80 may help to keep the coupling device 70 centered in the wellbore 100. Ports 40 may pass through one or more ribs 80, with blow-out plugs 50 seated in each port 40. In wells where cement casing is used, cement 110 fills the annular space exterior to the fluted coupling device 70. As the mechanically-induced weak points 200 are located on outward-facing surfaces 90 of the centralizer ribs 80, the mechanically-induced weak points 200 remain relatively close, if not adjacent, to the inner surface 120 of the wellbore 100, and thus close to the targeted rock formation 170. In some embodiments of the fluted coupling device 70, the blow-out plugs may be manufactured of soluble material, which may be selectively soluble, for example in acid-based solutions, as described above.

In the embodiment depicted in FIG. 6, the coupling device 130 comprises two burst discs 140 adapted to burst at a predetermined blow-out pressure differential. The burst discs 140 are each seated on an o-ring 150. In other embodiments, similar structures may be employed to prevent communication between the internal and external portions of the coupling device 130 while the burst discs 140 are seated.

Referring now to FIGS. 6, 7, and 8, in operation, the liner joint 10 or coupling device 30 or 130 is run in to the wellbore 100 to a predetermined depth. Generally, the predetermined depth corresponds to the location of a targeted rock formation 170. In cases where the operator wishes to access the targeted rock formation 170 at multiple depths, multiple liner segments 10 or liner joint coupling devices 30 or 130 are run to those depths.

As depicted in FIG. 6, internal liner packers 152 are located within a liner 300 to selectively straddle one or more mechanically-induced weak points 200, thereby hydraulically isolating the internal portion of the liner 300 that includes mechanically-induced weak points 200. The packers 152 may be mechanical, inflatable, swellable, or other known packer types to hydraulically isolate the internal portion of the liner 300 that includes mechanically-induced weak points 200.

In open hole wells, as depicted in FIGS. 7 and 8, the liner joint 10 or joint coupling device 30 is straddled with external open hole packers 160. The packers 160 may be mechanical, inflatable, swellable, or other known packer types to allow for isolation of individual sections of the wellbore 100.

Referring now to FIGS. 6, 7, and 8, after the packers 152 and 160 are activated, treatment fluid is pumped down the work string 155, which exits the fluid port 157 into the hydraulically-isolated portion of the liner 300. The treatment fluid is then pressurized until the pressure differential between the fluid in the liner 300 and the pressure external to the liner 300 exceeds the predetermined blow-out pressure differential of the mechanically-induced weak point 200. Upon exceeding the pre-determined blow-out pressure differential, the one or more mechanically-induced weak points 200 may burst, thereby allowing communication between the inside of the liner 300 and the targeted rock formation 170.

Certain mechanically-induced weak points 200 may be adapted to burst at higher or lower blow-out pressure differentials than other weak points 200. As a result, some weak points 200 may be selectively burst without bursting others. Further, pressures external to the liner may differ throughout the well; thus the pressure differential may vary even if the internal pressure is uniform. As will be recognized by one of ordinary skill in the art having the benefit of this disclosure, a mechanically-induced weak point 200 may be any structure, such as a burst disc 140, blow-out plug 50, or soluble plug 50 that is adapted to burst, rupture, or fail, thereby permitting communication between the inside and outside of the liner 300 at a predetermined pressure differential.

In operation of systems where one or more blow-out plugs 50 are manufactured from soluble material, for example an acid-soluble blow-out plug 50, a dissolving medium may be pumped down the well to the soluble plug 50, which may completely or partially dissolve one or more soluble blow-out plugs 50. Upon partial dissolution of the blow-out plugs 50, the dissolving medium or a different treatment fluid may be circulated at higher pressure to burst the partially-dissolved blow-out plugs 50 from the port 40, thereby permitting communication between the inside and outside of the liner 300.

In operation, after bursting one or more mechanically-induced weak points 200, the internal liner packers 152 may be deactivated and run to a new location in the liner 300, to straddle and selectively burst additional mechanically-induced weak points 200. Treatment fluid pressure inside the liner 300 is increased to burst the mechanically-induced weak point(s) 200 as described above. This process may be repeated as many times as desired or needed to burst multiple mechanically-induced weak points 200 installed in the wellbore 100.

Referring now to FIG. 5, prior to cementing operations, ports 40 may be filled with a viscous fluid, such as grease, to prevent the ingress of cement 110 thereinto. After cementing operations, the layer of cement 110 between the outward-facing surfaces 90 and the wellbore inner surface 120 may be relatively thin. Thus, when the mechanically-induced weak points 200 that are located on the outward-facing surfaces 90 burst, the treatment fluid may likewise burst the thin layer of cement 110 to allow communication to the targeted rock formation 170.

As will be understood by one of ordinary skill in the art having the benefit of this disclosure, after the mechanically-induced weak points 200 are burst or opened, access to the targeted rock formation 170 may allow treatment of the targeted rock formation 170 using methods already known in the art.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. Accordingly, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

1. A liner segment, the liner segment comprising: a wall, forming an inner bore and an outer surface; a mechanically-induced weak point on the wall adapted to rupture at a predetermined pressure differential between the inner bore and the outer surface; wherein the mechanically-induced weak point permits communication between the inner bore and the outer surface after the mechanically-induced weak point has ruptured.
 2. The liner segment of claim 1, wherein the mechanically-induced weak point is selected from the group consisting of a machined weakness, a blow-out plug, a burst disc, and a soluble plug.
 3. The liner segment of claim 1, wherein the mechanically-induced weak point further comprises a port adapted to permit communication between the inner bore and the outer surface.
 4. The liner segment of claim 1, wherein the liner segment comprises a coupling device.
 5. The liner segment of claim 1, wherein the liner segment further comprises centralizer ribs.
 6. The liner segment of claim 5, wherein the mechanically-induced weak point is located on an outward-facing surface of at least one centralizer rib.
 7. A liner segment, the liner segment comprising: a wall, forming an inner bore and an outer surface; a port on the wall adapted to permit communication between the inner bore and the outer surface; and a soluble plug adapted to selectively prevent communication through the port.
 8. The liner segment of claim 7, wherein the soluble plug comprises acid-soluble material.
 9. A method of well completion, the method comprising: hydraulically isolating an internal length of a wellbore liner that includes a mechanically-induced weak point; pumping a treatment medium into the hydraulically-isolated wellbore length; and increasing the pressure of the treatment medium within the hydraulically-isolated wellbore length to a predetermined pressure, thereby causing the mechanically-induced weak point to burst.
 10. The method of claim 9, further comprising: locating the wellbore liner segment having the mechanically-induced weak point at a location in the well.
 11. The method of claim 9, wherein the mechanically-induced weak point is selected from the group consisting of a machined weakness, a blow-out plug, a burst disc, and a soluble plug.
 12. A method of well completion, the method comprising: hydraulically isolating an internal length of a wellbore liner that includes a plug made of soluble material; and pumping a treatment medium into the hydraulically-isolated wellbore length, thereby causing the plug to partially dissolve.
 13. The method of claim 12, further comprising: locating the wellbore liner segment having the plug at a location in the well.
 14. The method of claim 12, wherein: the plug comprises an acid-soluble material; and the treatment medium comprises an acid-based solution.
 15. The method of claim 12, further comprising: increasing the pressure of the treatment medium within the hydraulically-isolated wellbore length, thereby causing the partially-dissolved plug to burst. 